The
Cavalli Liquid Gold holds legendary status within the personal audio community.
I remember when I first entered into the hobby the Liquid Gold felt like the
very definition of ultra-high-end unobtanium. Among many within the hobby, it
was considered the king of headphone amplifiers. My first encounter with the
Liquid Gold was at Rocky Mountain Audio Fest in
2015. I remember vividly how it
gave headphones a tremendous sense of body, a level of holographic imaging and
transparency I had never heard before. I later got an extended audition with it
when Cavalli asked me to write some impressions of the Liquid Gold, Glass and
Crimson for the community before what turned out to be their final production
run in 2016.

In a private setting, the Liquid Gold was even more
impressive. I noted, at the time, that its soundscape didn't seem to have any
outer edges – the instruments just floated in a wide-open space with an
unbelievable sense of transparency. I'd never heard anything like it. It was the
absolute definition of the oft-overused audiophile term "holographic." Now,
more than two years since Cavalli Audio closed its doors, founder Alex Cavalli
has teamed with Monoprice to resurrect the design of this legendary amp with the
Monoprice Monolith Liquid Gold X ($999).

This version is a bit different from the original, however,
sporting a much smaller design and an onboard DAC. The Gold X doesn't quite
sport the same unbelievable power as the original either, but with 3.9 Watts
into a 50 Ohm load, it has plenty of power to drive any headphone, including the
notoriously difficult HiFiMAN HE-6se. Like the original, the Liquid Gold X is a
fully differential balanced solid-state amplifier. All of the circuit topology
and component values are identical to the original Liquid Gold. When it comes to
inputs and outputs, things vary slightly. While the original sported a four-pin
balanced output and two 6.35mm outputs that could double as three-pin balanced
outputs, the Gold X has been paired down to a single four-pin balanced output
and a single 6.35mm unbalanced output.

In the back, the Gold X offers a variety of connections: a set
of dual three-pin balanced inputs, a set of unbalanced RCA inputs, a USB digital input, a
S/PDIF coaxial digital input, and a TosLink optical digital input. One button on the front
selects between balanced, unbalanced, and digital; while another selects between
the three digital input options. A third button on the front toggles between low
and high gain and the fourth button engages the power.

On the back, there is
also a switch to engage automatic shutoff, which will power down the amplifier
after it idles for about four hours or so without use. Like many other Cavalli
designs, the amplifier has a phase splitter in the signal path from the
single-ended input, allowing any of the five input options to output in full
balanced mode from the four-pin output. Also, like many other Cavalli designs,
the amplifier runs a startup sequence, which takes maybe half a minute or so to
complete. Once the startup sequence is done, the power light changes from red to
white and you're ready to rock and roll.

While the amplifier runs just a tiny bit little warm, it's
nothing compared to the original Liquid Gold, which could get pretty toasty. By
touch, I would say the Liquid Gold X runs just a few degrees cooler than its
sister amp, the Liquid Platinum. Certainly not warm enough to radiate in any
noticeable way.

But enough about the design. Let's get into the part everyone
is waiting for, the sound.

The Analog SectionThe first thing you notice when you plug into the Liquid Gold
X is the silent abyss of the background. Like the Platinum, the Gold X's power
supply has been moved off-board to a switch-mode power supply, which, no doubt
helps its incredibly low noise floor. It is phenomenally quiet for an amplifier
with this level of power. I was even able to drive IEMs off of it, without much
in the way of noise, until the pot was well past listenable volume. The only
catch there is there's not a lot of actual volume play with sensitive IEMs. This
amp was designed with full-size headphones in mind.

With full-size headphones, I found I had a little bit more
flexibility on the volume pot than on the Liquid Platinum, which is pretty hot
with a higher voltage balanced source. The Gold has just a touch more play, it
seems, aided by the presence of two gain setting options. While the Platinum
offers 5x gain, the Gold offers 4x and 6x, so there's slightly more flexibility
overall. If we're talking about volume position in terms of a clock (8 o'clock
position versus 9 o'clock position, etc.), I'd say the difference in low gain
versus the Platinum's volume pot is about 30 to 45 minutes of extra flexibility
in the low volumes.

It's not a ton, but it does give you more wiggle room overall.
It would have been nice if the 4x gain was even lower, but I found it to be
perfectly functional for the 300 Ohm headphones and planars that got the lion's
share of listening time with it. These are the same headphones I would have
chosen to pair with an original Liquid Gold, anyway. The sound itself is
signature Cavalli. There is a slight bit of extra meat and warmth in the lower
midrange down through the midbass, giving it the sweet, tubey sound made famous
by the original Liquid Gold. Like the original, it's also sweet and
non-aggressive through the upper midrange and treble. It's a very inviting,
characteristically "chill" sound – one that's extremely well-suited to
long listening sessions.

The soundscape is a good size in terms of both width and
depth, but even more impressive is the razor-sharp imaging. Sound locations are
extremely dialed in, which is an area that always impressed me about the
original Liquid Gold. If pressed, I would guess that it doesn't throw quite as
large of a stage as the original Gold, but I don't have one here to compare, so
I'll leave that up to the forums to figure out.

Digging deeper into the sound signature of the Gold X, I'd say
the mids are the star of the show here, and if you're the type of person who
likes a little tubey bloom, but doesn't want to get caught in the endless cycle
of tube rolling, I'd venture to say, this might be your best bet under $1000.
Nothing from the amp ever feels strained or fatiguing, it's just pleasant and
musical through and through.

Comparing against the Monoprice Monolith Liquid Platinum with
the classic hard-to-drive choice, the HiFiMAN HE-6se, showcased the differences
between the amplifiers quite clearly. Given the popularity of the Liquid
Platinum, this likely offers the best lens into many aspects of the Liquid Gold
X's sound. Listening to "Piggy (Nothing Can Stop Me Now" from Nine Inch
Nails' classic The Downward Spiral revealed several spots where the Gold
X surpassed the Platinum. The most noticeable difference came in terms of the
bass delivery. With the Gold X, each kick drum landed with a thunderous blast
that rattled my eardrums. Switching back to the Platinum, the kick drum
registered with a modest "thwack", registering only a fraction of the power.

Another difference I found was the depth layering. As the
keyboard enters in the second verse, the Gold X places it at a pinpoint distance
behind the other instruments, creating a real sense of magic. The Platinum's
placement is much hazier and generally flattened, in comparison. The same sounds
are present, but their definition and placement just comes off as a little
sloppy when put in direct comparison against the Gold X.

The third and most obvious difference in comparing the two
with the demanding HE-6se shows in the upper midrange and treble, where the Gold
X always keeps a firm grip of control. The Platinum comes off as thinner,
splashier and uncontrolled, pitted against the Gold X's iron grip. This,
combined with the greater impact and presence on the low end, causes the Gold X
to come off as a bit warmer overall. But if one dives just a little bit deeper
and analyzes the sound, the reality is, the Gold X is in much firmer command of
the driver, delivering a more even and accurate response.

Switching over to the easier-to-drive 300 Ohm ZMF Verité
Closed, the differences become far less pronounced. The easiest way to compare
here would be to say the Gold X more or less sounds like a Liquid Platinum with
a really sweet set of tubes. Pitted against the Platinum with an early 1960's
set of Harleen-manufactured Dario Miniwatt 188CC's, the amplifiers finished in a
dead heat. That being said, a pair of cherry 6922-equivalent tubes (CCA, 188CC,
etc.) plus the price of their Platinum could very well run you nearly as much or
more than a Liquid Gold X. Given the additional digital inputs, extra gain
flexibility, additional driving power and extra refinement with more challenging
headphones – simply buying a Liquid Gold X seems like a more practical
alternative, rather than trying to incrementally upgrade to the same level
through tube rolling.

The Digital SectionThe DAC is a solid and convenient addition to the total
package of the Monoprice Monolith Liquid Gold X. While it didn't quite reach the
level of the Chord Hugo 2 that I primarily used to independently test the analog
section, that DAC sells for 2.5X the price of the Liquid Gold X ($2,495 versus
$999), so it's not a very fair comparison. The Hugo 2 had greater clarity,
deeper resolution, a more open stage and a richer, more analog sound overall, in
terms of the DAC. In terms of driving headphones directly, I'd probably prefer
the Gold X's extra bit of personality and musicality for most headphones as
opposed to the Hugo 2's somewhat dry direct-driving delivery.

Comparing against the excellent FiiO M15 ($1299), which is
also here for review, with the Gold X registering much closer. Both feature an
AKM chipset – 4493 for the Gold X and 4499EQ for the M15. The sound of both
DACs through the Gold X's amplifier section was nearly indistinguishable, though
I felt the FiiO M15 had a very, very slight edge in the deepest resolution in
the individual notes. Drums just came off as a hair more organic through the
M15. Could I pick this out in a blind test? Probably not. Given how close they
are, it was more or less a wash, which is to say the Gold X's built-in DAC is
pretty good overall.

All things considered, I feel that the DAC is a great
addition, particularly for the convenience factor. But just like you'd expect
from a similarly-priced integrated amplifier, the DAC section can certainly be
bested with a good standalone device. Some listeners may find a standalone DAC
to be a proposition of diminishing returns, given the agreeable sounding and
high-quality DAC integrated here. Others may find they want to push the Gold X
to the farthest edges of its capabilities. The fact that you have a choice in
the matter is a win.

Final ThoughtsThe Monoprice Monolith Liquid Gold X is simply a fantastic
piece, top to bottom. It sounds great, drives anything, and can serve as either
an all-in-one or a badass amplifier to anchor your system. Is it a mandatory
upgrade for owners of the Liquid Platinum? That's hard to say. It is a slightly
better amplifier overall. If you're looking for more out of the Platinum and are
reluctant to jump into the rabbit hole of tube rolling, then I'd say yes. The
Gold X will push you just past the edges of what tube rolling can offer with the
Platinum. Also, if you're using the Platinum with an entry-to-mid level DAC, the
all-in-one capability should provide you with a nice upgrade across the board.

If you're not a Platinum owner, or you're getting into Cavalli
gear for the first time, I would say that this is a great piece that exemplifies
the tubey and musical Cavalli sound signature. With a drier or more neutral type
of headphone, like the Sennheiser HD800, this can take your musical enjoyment up
several notches, as your tunes gain a bit more natural warmth and body without
losing their pinpoint accuracy.

Overall, this is an excellent all-around piece and a
phenomenal value sitting just under $1000. If you have the opportunity to hear
one, it's a must audition.